Implantable medical device having flat electrolytic capacitor with tailored anode layers

Abstract

Flat electrolytic capacitors and methods of making and using same in implantable medical devices (IMDs) are disclosed, the capacitors having a plurality of capacitor layers of an electrode stack formed of tailored numbers of anode and cathode layers to fill the available stack height space in the capacitor case. The capacitor is formed with a capacitor or electrode stack assembly having a stack assembly thickness or height HN that is tailored to fit a case wall height Hcw of the capacitor case with minimal wasted space and allowance for any stack height tolerance to. The electrode stack assembly comprises a plurality of N stacked capacitor layers each having a specified capacitor layer thickness or height. At least N1 capacitor layers have a first capacitor layer thickness T1 and N2 capacitor layers have a second capacitor layer thickness T2 where N=(N1+N2), and HN=N1*T1+T1*N2. The N capacitor layers are preferably formed of a cathode layer, and anode sub-assembly and at least one separator layer comprising one or more separator sheet on either side of the cathode layer and the anode-layer sub-assembly. The anode sub-assemblies of the N1 capacitor layers comprising x anode layers each having anode layer thickness tx stacked together, each anode layer having an anode layer thickness Tx. The anode sub-assemblies of the N2 capacitor layers comprising y anode layers each having anode layer thickness ty stacked together, each anode layer having an anode layer thickness Ty.

We claim:  
     
       1. An implantable medical device comprising: 
       a housing;  
       an electronics module disposed within the housing;  
       an energy source disposed within the housing and electrically coupled to the electronics module; and  
       an optimally sized capacitor assembly disposed within the housing and electrically coupled to the electronics module, the capacitor assembly further comprising:  
       a sealed capacitor case defining an interior case chamber of pre-existing dimension, the case having a base having a base peripheral edge, a case side wall extending between the base peripheral edge to a side wall opening edge defining a case opening edge, and a cover sealed against the case opening edge to enclose the interior case chamber, whereby the interior case chamber has a case chamber periphery and a case chamber height H cw ; and  
       an electrode stack assembly optimally sized to be located within the interior case chamber comprising N capacitor layers stacked in registration upon one another and between the case base and the cover having a stack height H N  selected to be equal to or less than the case chamber height H cw  by a predetermined tolerance,  
       wherein N 1  capacitor layers of the N capacitor layers each have a first capacitor layer thickness T CL1  and each further comprise:  
       a cathode layer having a cathode layer thickness and a cathode peripheral edge extending toward the case side wall throughout a major portion of said case chamber periphery and having a cathode tab extending toward the case side wall in a minor portion of said case chamber periphery;  
       an anode sub-assembly comprising x anode layers each having anode layer thickness t x  and an anode layer peripheral edge extending toward the case side wall throughout a major length of said base peripheral edge, whereby each anode sub-assembly has an anode sub-assembly thickness T x  and further comprises an anode tab extending toward the case side wall in a minor portion of said case chamber periphery; and  
       a plurality of electrolyte bearing separator layers each having a separator peripheral edge extending toward the case side wall, the electrolyte bearing separator layers disposed on each side of the anode sub-assembly and the cathode layer of the capacitor layer,  
       whereby the first capacitor layer thickness T CL1  is dependent upon the thickness of the plurality of separator layers, the cathode layer thickness and the anode sub-assembly thickness T x ; and  
       wherein N 2  of the N capacitor layers each have a second capacitor layer thickness T CL2  and each comprise:  
       a cathode layer having a cathode layer thickness and a major cathode peripheral edge extending toward, but spaced from, the case side wall a distance D 2  throughout a major portion of said case chamber periphery and having a cathode tab extending toward the case side wall in a minor portion of said case chamber periphery;  
       an anode sub-assembly comprising y anode layers each having anode layer thickness t y  and an anode layer peripheral edge extending toward, but spaced from, the case side wall a distance D 1  throughout a major length of said base peripheral edge, whereby each anode sub-assembly has an anode sub-assembly thickness T y  and further comprises an anode tab extending toward the case side wall in a minor portion of said case chamber periphery; and  
       a plurality of electrolyte bearing separator layers each having a separator peripheral edge extending toward, and abutting the case side wall over a majority of the separator peripheral edge, the electrolyte bearing separator layers disposed on each side of the anode sub-assembly and the cathode layer of the capacitor layer,  
       whereby the second capacitor layer thickness T CL2  is dependent upon the thickness of the plurality of separator layers, the cathode layer thickness and the anode sub-assembly thickness T y ;  
       wherein the distance D 1  is approximately equal to the distance D 2 ; and  
       whereby the stack height H N  is dependent upon N 1 *T CL1 +N 2 *T CL2 .  
     
     
       2. The implantable medical device of  claim 1 , wherein the number of x anode layers is not equal to the number of y anode layers. 
     
     
       3. The implantable medical device of  claim 1 , wherein the anode layer thickness of t x  is equal to the anode layer thickness t y , and the number of x anode layers is not equal to the number of y anode layers. 
     
     
       4. The implantable medical device of  claim 3 , wherein the x anode layers comprise at least two anode layers and the y anode layers exceed the number of x anode layers and the x anode layers are interposed between the y anode layers. 
     
     
       5. An electrolytic capacitor assembly comprising: 
       a sealed capacitor case defining an interior case chamber, the case having a base having a base peripheral edge, a case side wall extending between the base peripheral edge to a side wall opening edge defining a case opening edge, and a cover sealed against the case opening edge to enclose the interior case chamber, whereby the interior case chamber has a case chamber periphery and a case chamber height H cw ; and  
       an electrode stack assembly located within the interior case chamber comprising N capacitor layers stacked in registration upon one another and between the case base and the cover having a stack height H N  selected to be equal to or less than the case chamber height H cw  by a predetermined tolerance,  
       wherein N 1  capacitor layers of the N capacitor layers each have a first capacitor layer thickness T CL1  and each further comprise:  
       a cathode layer having a cathode layer thickness and a cathode peripheral edge extending toward, but spaced from, the case side wall a distance D 2  throughout a major portion of said case chamber periphery and having a cathode tab extending toward the case side wall in a minor portion of said case chamber periphery;  
       an anode sub-assembly comprising x anode layers each having anode layer thickness t x  and an anode layer peripheral edge extending toward, but spaced from, the case side wall a distance D 1  throughout a major length of said base peripheral edge, whereby each anode sub-assembly has an anode sub-assembly thickness T x  and further comprises an anode tab extending toward the case side wall in a minor portion of said case chamber periphery; and  
       a plurality of electrolyte bearing separator layers each having a separator peripheral edge extending toward the case side wall and abutting said case side wall over a majority of said separator peripheral edge, the electrolyte bearing separator layers disposed on each side of the anode sub-assembly and the cathode layer of the capacitor layer;  
       whereby the first capacitor layer thickness T CL1  is dependent upon the thickness of the plurality of separator layers, the cathode layer thickness and the anode sub-assembly thickness T x ; and  
       wherein N 2  of the N capacitor layers each have a second capacitor layer thickness T CL2  and each comprise:  
       a cathode layer having a cathode layer thickness and a cathode peripheral edge extending toward, but spaced from, the case side wall the distance D 2  throughout a major portion of said case chamber periphery and having a cathode tab extending toward the case side wall in a minor portion of said case chamber periphery;  
       an anode sub-assembly comprising y anode layers each having anode layer thickness t y , and an anode layer peripheral edge extending toward, but spaced from, the case side wall the distance D 1  throughout a major length of said base peripheral edge, whereby each anode sub-assembly has an anode sub-assembly thickness T y  and further comprises an anode tab extending toward the case side wall in a minor portion of said case chamber periphery; and  
       a plurality of electrolyte bearing separator layers each having a separator peripheral edge extending toward the case side wall, the electrolyte bearing separator layers disposed on each side of the anode sub-assembly and the cathode layer of the capacitor layer;  
       whereby the second capacitor layer thickness T CL2  is dependent upon the thickness of the plurality of separator layers, the cathode layer thickness and the anode sub-assembly thickness T y ;  
       wherein the distance D 1  is approximately equal to the distance D 2 ; and  
       whereby the stack height H N  is dependent upon N 1 *T CL1 +N 2 *T CL2 .  
     
     
       6. The capacitor of  claim 5 , wherein the number of x anode layers is not equal to the number of y anode layers. 
     
     
       7. The capacitor of  claim 5 , wherein the anode layer thickness t x  is equal to the anode layer thickness t y , and the number of x anode layers is not equal to the number of y anode layers. 
     
     
       8. The capacitor of  claim 7 , wherein the x anode layers comprise at least two anode layers and the y anode layers exceed the number of x anode layers.